Fire ants interfere with hay harvesting, maintenance of pastures and some crops, but present the greatest problem around human dwellings. The greatest danger arises from multiple stings, often experienced by young children.

The two most common forms of imported fire ants are the red imported fire ant and the black imported fire ant. The black fire ant was introduced into Alabama from South America in 1918 and remained confined to the immediate area for about 10 years. The red imported fire ant was introduced into Alabama about 1930 and has since spread to the outer limits of the present imported fire ant range. There has been much controversy over the taxonomic status and interrelationship of the light and dark forms or species.

Distribution

The red imported fire ant is more widespread and is now in much of the Southeast, from the Carolinas to Texas. The imported red fire ant has invaded over 275 million acres. All counties in Alabama, Florida, and Louisiana are infested. Counties in Arkansas, Georgia, Mississippi, Oklahoma, North Carolina, South Carolina, Tennessee, and Texas plus Puerto Rico have been invaded. Isolated colonies have been found as far west as California, and as far north as Kansas City, Missouri. One factor accounting for the rapid spread of fire ants in a region is the transport of queens and colonies by movement of nursery stock.

Stings

Their sting is characterized by an intense burning sensation. A pustule (not seen in the sting of other species) forms at the sting site in a day or so and may become infected. Sensitive individuals may swell up as a result of stings and occasionally die. The venom of fire ants, containing alkaloids with relatively little protein, is unique among stinging insects, who usually employ a venom rich in protein. The venom is used to kill prey for food. It is an effective agent in killing insects, bacteria, and fungi.

Feeding Habits

Food is collected by workers who often leave the mound through tunnels which extend 15-25 m from the mound, 6-12 m underground. When food is found, the forager returns to the nest, leaving a pheromone trail for others to follow to the food source.

Their primary food is insects such as spiders, earthworms, fly larvae in animal wastes, leaf-eating caterpillars, and other ground-crawling insects. They attack newly hatched poultry and the young of ground-nesting wild birds. Helpless newborn animals, domestic and wild, have been killed by swarms of the worker ants.

Insects, spiders, myriopods, earthworms, and other small invertebrates make up the usual diet of the fire ants. They are attracted to sugar and honeydew and are known to feed on carrion.

Colonies

A colony is usually started by a single queen, but some beginning colonies are known to contain up to 5 queens. Fire ants infest lawns, school yards, athletic fields and parks. They invade household kitchens and pantries. Mature multi-queen colonies are generally the case. After the nuptial flight, the queen lays eggs in the burrow she has created in 24-48 hours, the first workers appear 20-30 days later. Reproductive forms are produced in 5-12 months. A colony may contain 240,000 workers after three years. Each colony of fire ants is composed of a queen, winged males and females, and three kinds of workers. A single nest averages approximately 25,000 workers, but far larger populations are common.

The semipermanent nests are large, unsightly mounds of excavated soil with openings for ventilation. Imported red fire ant mounds are generally dome-shaped, in contrast to those of other fire ant species. The hardened mounds interfere with the mechanical cultivation of fields and the ants' painful stings interfere with livestock grazing and the harvesting of crops by farm workers. The ants nest in the soil of open areas, pastures, agronomic fields, and are found occasionally in wooded areas.

Regulation

In 1958, a federal quarantine was enacted to try to prevent the fire ant's spread. The quarantine restricts the movement of soils, sod, hay, potted plants, plants with soil attached, and used soil-moving equipment to uninfested areas. These pests are regulated in several States, including: Alabama, Florida, Louisiana, and parts of Arkansas, Georgia, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, and Texas.

Control

The problem of effectively eradicating fire ants has baffled scientists and the government for decades. Control tactics include the judicious use of pesticides and other management options. Biological control has become an area of interest within the community of fire ant researchers. There are parasitic flies, ants, and other organisms that are currently being evaluated for use in fire ant infested areas of the United States.

One solution under investigation is infesting fire ants with the microorganism T. solenopsae. In 1973, it was discovered in Brazil and is the most common pathogen found in fire ants in South America. The pathogen T. solenopsae infects ant colonies and chronically weakens them. The microorganism doesn't harm plants or native ant species. Workers transmit the pathogen to the queen through food exchange. The disease slowly reduces her weight. She lays fewer and fewer eggs, all infected with the pathogen, further weakening the colony. Colony elimination can take from nine to 18 months.

Fire ants infected with a microorganism were released in Arkansas and Oklahoma to reduce the numbers of the imported ants. Scientists from the U.S. Department of Agriculture's Agricultural Research Service think that, over time, T. solenopsae can reduce fire ant populations.

Community Involvement Needed for Successful Abatement

Community involvement is important for effective control of the red imported fire ant. Several communities throughout the United States have developed abatement programs to minimize the impact of this insect. There are several types of abatement programs which a community can develop. Some communities have area-wide treatment periods during which the homeowner elects to purchase the appropriate pesticide and apply it within a specified period. Other communities involve individuals who apply the pesticides at the appropriate period, and the community pays him/her a fee for services.

In 1997, Texas offered a $1,000 reward for the discovery of the largest fire ant mound to stimulate the public and press to become aware of the threat of imported red fire ants. The contest was divided into two categories, the largest city mound and the largest country mound. The largest mound found was 40 inches at the base and 18 inches tall. According to Texas surveys, fire ants are considered the second most important urban pest, behind cockroaches. Besides stinging people and animals, fire ants can damage air conditioners, outside lighting, sprinkler systems, computers and other electronic equipment.